Wood Frog

Next week I will take Saturday off for Christmas. On January 2nd, the next Saturday, I will post an animal fact on Facebook instead of my normal post. If you have not already liked Next Door Zoo on Facebook, click here to do that now so you won’t miss it! Don’t forget to share next door zoo with your family and friends over Christmas!

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Wood frogs are medium-sized amphibians living throughout the United States and Canada. These frogs vary in color from reds, to gray, to browns. Their belly is usually white. If you look at the skin of the frog pictured above, you can probably tell how this frog got its name. It almost looks like the bark on a tree. By its back leg there is even a patch that almost looks like lichen! Behind the eyes there are brown patches. These patches aren’t brown in every wood frog, but each one does have a darker patch in the same place. This marking, sometimes called a “robber’s mask” is one of the distinguishing features of wood frogs. In the “robber’s mask,” behind the eye, you can see a faint circle. This is the frog’s tympanum, or outer ear. Extending from the eye to the back leg is a ridge that makes this frog look boxier than most.

Size

These small frogs can be as small as 1.4 inches (3.5 cm) in length or up to 3.3 inches (8.3 cm) long. As you can see this is quite a big range, with the larger being twice as long as the smaller length! They can weigh up to 0.3 ounces (8 grams). To give you an idea of how light this is, TWO wood frogs would weigh about as much as just ONE CD or DVD! Females are generally larger than males.

Diet

Adult wood frogs are insectivores eating a variety of insects as well as slugs, worms, snails, and spiders. Some of their favorite insect foods are beetles and caterpillars. Their tadpoles are mainly herbivores consuming algae and decaying plant matter. They will also eat decaying animal matter or the eggs and tadpoles of other amphibians.

Habitat and Range

Wood frogs live farther north than any other North American reptile or amphibian! As you can see on the map, they even live in some of the most northern places in Alaska! The range map shown below is not actually exactly accurate as there are reports of them living as far south as northern Georgia and as far west as Idaho in the United States. The name wood frog probably leads you to believe that these frogs live in the woods, but that is not always correct. Although their main habitat is woodlands and forests, they also live in meadows, bogs and even tundras with very little vegetation. When it is not breeding season, these little frogs live under fallen logs or leaves, which provide them shelter from predators.

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Surviving the cold

Because they live so far north, wood frogs must have some way to cope with the extremely cold winter weather. During their winter hibernation, these frogs can survive a sustained body temperature of as low as 21 °F (-6 °C)! They are able to do this in part due to a special protein in their blood. Because I don’t want to bore you, and I don’t have a PhD in chemistry, I won’t go into all the details about how this works. The simple description of this protein’s job is that it prevents ice crystals from forming. While they are hibernating, blood flows mainly to the liver and brain. The liver also releases a large amount of glucose. This helps reduce ice that forms on the frog’s cells.

Status, threats, and protection

Although they have many natural predators, wood frogs are classified as “Least Concern” by IUCN. Some of their enemies in the wild are snakes, herons, raccoons, and skunks. The young are sometimes preyed on by aquatic insects and newts. Wood frog eggs may be consumed by leeches, newts, and aquatic insects as well. One of the wood frog’s forms of protection is their camouflage coloring that I described in the first paragraph. They also have slimy skin that sometimes lets them slip out of a predator’s grasp. If this doesn’t work, they will make a piercing cry that will hopefully startle the predator into releasing the frog.

Mating, eggs, and tadpoles

Wood frogs take part in what is called “explosive breeding.” During the mating season, which is from March to May, all the adults get together at near-by ponds where they all race to find a mate. The idea behind this type of breeding is that with so many individuals together, it is more likely that each one will find a suitable mate. The males make a duck-like call to attract a suitable female. You can listen to this call below.

After mating, the females lay a huge glob of eggs. Each mass can contain up to 3,000 eggs! A while after the eggs are laid, the jelly around the eggs turns green due to algae growing on it. This is actually helpful because it camouflages the vulnerable eggs with the surrounding aquatic plants. Nine to thirty days later, the eggs hatch. The tadpoles will undergo metamorphosis when they are two months old. Males are ready to mate between one and two years of age, but females take about a year longer. These frogs can live up to five years in the wild.

Don’t forget to scroll down and comment your guess about what the animal for January 9th is!

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Sources:

Photo credits:

  • Wood frog – W-van
  • Wood frog range – Craig Pemberton
  • Wood frog call – D. Gordon E. Robertson
  • Mystery animal – Kmanoj

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